Brake disk for a disk brake

ABSTRACT

The invention relates to a brake disc for a rail vehicle, with which a hub body ( 16 ) and a brake ring ( 12 ) are connected to one another such that with braking procedures a thermal expansion of the brake ring ( 12 ) relative to the hub body ( 16 ) is possible. At the same time screws ( 15 ) pass through axially aligned openings in a hub flange ( 14 ) arranged on the hub body ( 16 ) and a brake ring flange ( 13 ) arranged on the brake ring ( 12 ). According to the invention the screws at their end exiting the brake ring flange ( 13 ), by way of a retaining element which e.g. may be a retaining lug ( 17 ) formed integrally on the hub body ( 16 ) or a retaining bracket fixed on the hub body, may be fixed relative to the hub body ( 16 ) so that an axially parallel position of the screws ( 15 ) and a centering of the brake ring ( 12 ) is ensured even with thermal expansions. The mounting of the screws ( 15 ) is effected indirectly via an axially displaceably movable sleeve ( 20 ) or by a retaining braket engaging into a groove on the hub. Furthermore there are provided radial guides for the brake ring ( 12 ) which e.g. may be realised e.g. by the guiding of the sleeve ( 20 ) in a slide block.

TECHNICAL FIELD

[0001] The invention relates to a brake disc for a disc brake, inparticular for rail vehicles. This contains a hub body with a radiallyoutwardly extending hub flange with axially parallel openings in whichscrews may be arranged in order to connect a brake ring flange of abrake ring to the hub body, said brake ring flange being arrangedradially overlapping and axially adjacent the hub body. It furtherrelates to a brake ring for a disc brake, in particular for railvehicles containing a radially extending brake ring flange with axiallyparallel openings in which screws may be arranged in order to connect ahub flange of a hub body to the brake ring, said hub flange beingarranged radially overlapping and axially adjacent the brake ringflange.

STATE OF THE ART

[0002] Disc brakes of the above mentioned type are for example knownfrom DE 26 20 623 A1 (FIGS. 1 and 2). They consist of a hub body whichis arranged in a rotationally fixed manner on the shaft of the axle of avehicle, as well as a brake ring connected to the hub body. The brakering on at least one outer side comprises a friction surface on whichbrake shoes engage and by way of a suitable pressure on the frictionsurface may exert the desired braking effect. The connection between thehub body and the brake ring is effected via a screwing of the hub flangewith the brake ring flange. The mentioned flanges are radially distantfrom the hub body or brake ring, overlap in the radial direction and arearranged axially adjacent one another. The details “radial” and “axial”or “axially parallel” relate to the rotational axis of the brake disc(the same as the axis of the shaft on which the brake disc is attached),which as a rule is also an axis of symmetry of the brake disc.Furthermore the flanges may be designed peripherally in a continuousmanner as well as peripherally in a wave-like manner, wherein in thelatter case they consist of adjacent lugs. The screws for fastening thebrake ring on the hub body pass through openings in the hub flange andin the brake ring flange, these openings being essentially aligned toone another.

[0003] It is known that with disc brakes of the mentioned type, withbraking procedures the brake ring expands on account of the occuringheating, whereas the hub body does not experience any comparableexpansion. A multitude of designs are known for accommodating or forcompensating the thermal expansions occuring between the hub flange andthe brake ring flange.

[0004] Thus for example DE-B 10 31 337 shows a disc brake of the abovementioned type with which the screwing between the hub flange and thebrake ring flange is designed such that a radial relative movementbetween both bodies is possible. In particular there are provided radialslots in the brake ring flange distanced equally over the circumferencein which the screws which pass through it may travel radially. Howeverwith such a design there exists the danger that with thermal expansionsthe screws may lose their parallel position to the axis of the discbrake. Thus for example the screw heads may retain their positionrelative to the hub flange on which they rest, whilst the screw sectionlies in the brake ring flange and is displaced radially outwards by thison thermal expansion. This leads to considerable bending stresses of thescrews which may lead to an increased wear, premature fatigue and in theworst case to a failure of the screws.

[0005] For reducing the mentioned bending stresses of the screws, inDE-A 28 28 137 it is known in a disc brake of the initially mentionedtype to mount the screw heads as well as nuts in spherical bearingshells, by which means the screws may be pivoted out of their axiallyparallel bearings essentially without bending and shear stresses. Thisembodiment form however is very complicated and thus expensive and withthermal expansions leads to undesired changes in the pretension of thescrews.

[0006] From DE 34 32 501 C2 there is further known a disc brake of theinitially mentioned type with which the brake ring flange is arrangedmovable with thermal expansion between the hub flange and a separatetension ring, wherein the screws axially tension the hub flange againstthe tension ring. The respective ends of the screws are thus mounted inthe hub flange or in the tension ring and thus in two elements which asa rule are not subjected to a relative movement on thermal expansion. Itis however disadvantageous that additional means for torque transmissionmentioned type to mount the screw heads as well as nuts in sphericalbearing shells, by which means the screws may be pivoted out of theiraxially parallel bearings essentially without bending and shearstresses. This embodiment form however is very complicated and thusexpensive and with thermal expansions leads to undesired changes in thepretension of the screws.

[0007] From DE 34 32 501 C2 there is further known a disc brake of theinitially mentioned type with which the brake ring flange is arrangedmovable with thermal expansion between the hub flange and a separatetension ring, wherein the screws axially tension the hub flange againstthe tension ring. The respective ends of the screws are thus mounted inthe hub flange or in the tension ring and thus in two elements which asa rule are not subjected to a relative movement on thermal expansion. Itis however disadvantageous that additional means for torque transmissionmust be provided between the hub body and the tension ring so that nobending stresses of the screws occur perpendicular to the radialdirection. On account of these means the constructional effort isincreased and the assembly is made more difficult. With disc brakesventilated at the inside, the tension ring may considerably handicap thesupply of cooling air to the brake disc. Furthermore there also existsthe possibility that with thermal expansion, the forces on the tensionring occur assymetrically with respect to the rotational axis of thedisc brake and that on account of this the undesired bending stressesindeed do arise.

[0008] From DE-OS there is known a multi-part brake disc with which on ahub there are provided radially outwardly extending lugs which haveaxially parallel openings in order to fasten an overlappingly arrangedlug of a brake ring by way of corresponding screws, wherein in each casetwo lugs distanced from one another are in each case provided with anopening through which the ends of the screw may be held. At the sametime one envisages designing the fastening screws for the brake ringconsisting of brake ring elements as fitting bolts. In order to designthe screw connection such that it is axially free of play, may bereadjusted in limits and additionally is tensionally locked, at the sametime each lug is tensioned against the end face of the hub via bushings.

DESCRIPTION OF THE INVENTION, OBJECT, SOLUTION, ADVANTAGES

[0009] Against this background it was the object of the presentinvention to improve a hub body, a brake ring and a brake disc of theinitially mentioned type with simple design means in a manner such thatwith thermal expansions of the brake the axial parallelity of the screwswhich connect to brake ring flange to the hub flange is ensured.arranged a retaining element with all, but at least with three openingsarranged distributed over the circumference.

[0010] With the brake disc according to the invention thus both ends ofthe screws which connect the hub flange to the brake ring flange arefixed relative to the hub body. The first end of the screw which may forexample be the screw head, is mounted in an opening on the hub flange.The screw then passes through the brake ring flange, and its second endis held in the retaining element which is fixed on the hub body andtransmits this fixation onto the end of the screw. By way of the radialfixing of the screws at both ends their axially parallel position isensured even with thermal expansions of the brake ring. This is also thecase with the use of several retaining elements if the forces should notoccur symmetrically with respect to the rotational axis of the brakedisc. By way of radial guides according to claim 4 it is ensured thatthe brake ring always remains centred relative to the axis of the brakedisc even with thermal expansions.

[0011] According to a first embodiment form of the retaining elementsaccording to the invention these may be designed as a radially outwardlyextending retaining lug or as a circumferential retaining flange on thehub body. The formation of the retaining element as a retaining lug onthe hub body has the advantage that between two such lugs there remainsa free space through which cooling air may flow during operation.Furthermore on assembly of the brake disc, in a simple manner a likewiselug-shaped designed brake ring flange may be introduced through the freespace into the intermediate space between the hub flange and theretaining elements. The integral formation of the retaining element withthe hub body simplifies the assembly of the brake disc since theretaining elements do not need to be assembled separately.

[0012] In a further formation of the last mentioned embodiment form theretaining element formed on the hub body may comprise an axiallyparallel opening with a sleeve arranged therein, wherein the opening inthe retaining element is arranged aligned to the corresponding openingin the hub flange. A screw passing through the hub flange and thebraking ring flange may be led through the sleeve, wherein the sleeve isthen supported on one side on the braking ring flange. The sleeve servesfor pretensioning the brake ring against the hub flange. This,iseffected via the support of the sleeve on the brake ring flange, whereinon the opposite end of the sleeve the screw engages on the screw threadvia the screw head or the nut. By way of the mounting in the sleeve thescrew at the same time is additionally protected from bending stresses.By way of the fact that the sleeve is arranged in the opening of theretaining element, furthermore an indirect radial fixing of the screwend relative to the hub body is achieved. At the same time the sleevehowever remains axially parallel displaceable in the opening of theretaining element, so that it may transmit the desired axial pretensionforce onto the brake ring flange.

[0013] According to a further formation of the above mentionedembodiment form, on the hub flange and/or on the retaining elementsthere are provided at least three radial guides equally distributed overthe cicumference, which may cooperate with corresponding radial guideson the brake ring flange, in order in the case of a thermal expansion toradially guide and, centre the brake ring flange. The equal distributionof the radial guides over the circumference means that for example threesuch radial guides at a distance of in each case 120° are arrangedaround the rotational axis of the disc brake. The radial guides ensurethat although the brake ring may move in the radial direction relativeto the hub body and thus may follow a thermal expansion, however norelative rotation of the brake ring about the rotational axis of thebrake disc is possible and that the torque transmission between thebrake ring and hub body and their relative position in thecircumferential direction remains ensured. Simultaneously the radialguides pointing in various radial directions ensure that the brake ringand hub body assume a centered position to one another also with athermal expansion.

[0014] The above mentioned radial guides in each case are preferablyformed as two surfaces extending parallel to a radius on the hub flangeand/or on a retaining element, which cooperate with correspondingsurfaces on the brake ring flange. The extension of the surfacesparallel to a radius proceeding from the rotational axis of the discbrake ensures that the surface exerts a guide in the direction of thisradius.

[0015] According to a second design form of the retaining element of thepresent invention, this is formed as an L-shaped retaining bracket whichin a first limb comprises an opening for leading through..the end, ofthe screw. Furthermore on the hub body there is provided an axiallyorientated groove in which the second limb of the mentioned retainingbracket may be arranged. The orientation of the groove is defined as thedirection from the base of the groove towards its opening, that is tosay parallel to the walls of the groove. Of course this embodiment formof the retaining elements may also be combined with the above explainedform since the individual retaining elements distributed along thecircumference of the hub body are basically independent of one another.The L-shaped retaining bracket is mounted in the axially orientatedgroove on the hub body in a manner such that it remains movable in theaxial direction and is fixed in the radial direction as well aspreferably also in the circumferential direction. As a whole then thedesired radial fastening of the retaining bracket is achieved, whereinthe retaining brackets however simultaneously with the tightening of thescrews move axially and thus may transmit the set pretension force ontothe brake ring flange. The use of retaining brackets has the advantagethat on assembly of the disc brake these may firstly be removed so thatthe brake ring and disc body may be put together in an unhinderedmanner. Only on tightening the screws are the retaining brackets thenattached after one another. Furthermore by way of the application of thevariously dimensioned retaining brackets there may be effected a simpleadaptation of the dimensions of the brake ring and hub body.

[0016] The invention furthermore relates to a brake ring for a discbrake, in particular for rail vehicles, containing a radially extendingbrake ring flange with axially parallel openings in which there may bearranged screws in order to connect a hub flange arranged radiallyoverlapping and neighbouring the brake ring flange to the brake ring.The brake ring is characterised in that with at least one opening thereis arranged a retaining element which is fixed on the brake ring and byway of which the end of the screw may be held after its passage throughthe hub flange.

[0017] With such a brake ring the two ends of the screws are fixedrelative to the brake ring. The brake ring on construction of the discbrake therefore functionally behaves in the same manner as the aboveexplained hub body. The possibilities of design of the hub bodyexplained above may thus be accordingly applied to the brake ring.

[0018] Furthermore a brake disc, in particular a brake disc for railvehicles, containing a hub body as well as a brake ring fastened tothis, also belongs to the invention. The brake disc is characterised inthat the hub body is designed in the manner explained above and/or inthat the brake ring is designed in the manner explained above, and thatthe end of the screw is held by the retaining element fixed on the hubbody or on the brake ring. With such a brake disc by way of the fixationof the screw ends on both sides it is ensured that the screws retaintheir axially parallel position even with a thermal expansion of thebrake ring and, the screws as well as the brake ring remain centeredwith respect to the axis of the disc brake. Furthermore as explainedabove with reference to the hub body, one achieves a simplification ofthe assembly as well as a guarantee of the ventilation of the brakering.

[0019] According to a further embodiment form it is envisaged for thescrew to be designed such that firstly the head has a surface which byway of its bearing an a collar of the hub formed specially as a support,there is effected a rotational securement when screwing the nut on andoff, and secondly below the head there is incorporated a knurling whichon assembly of the screw into the hub digs into the receiver bore and byway of this firmly retains the screw with a press fit in the hub so thaton assembly of the brake ring it does not need to be held in position byhand.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the following the invention is explained by way of examplewith the help of the figures. There are shown in:

[0021]FIG. 1 a cross section through the screw connection of a hub bodywith a brake ring as well as perspectively the sleeve used in this;

[0022]FIG. 2 a cross section through an embodiment example modified withrespect to FIG. 1, and a slide block;

[0023]FIG. 3 a cross section through a further modified embodiment formand a perspective view of a retaining bracket used therein;

[0024]FIG. 4 a plan view of a brake disc composed of the hub body andbrake ring with the surface of the brake ring partly broken;

[0025]FIG. 5 a cross section along line V-V of FIG. 4,

[0026]FIG. 6 the hub body according to FIG. 5,

[0027]FIG. 7 a part view of the hub body according to arrow VII in FIG.6, and

[0028]FIG. 8 an enlarged part representation of the hub body accordingto FIG. 6.

BEST WAY OF CARRYING OUT THE INVENTION

[0029] In FIG. 1 there is shown a cross section through the screwconnection between the hub body 16 and the brake ring 12. The hub body16 is arranged on the shaft of the axle of a rail vehicle (not shown) ina rotationally fixed manner and is connected to the brake ring 1 in arotationally fixed manner. The brake ring 12 on one or on two sidescomprises friction surfaces (not shown) on which brake shoes may engagefor producing the braking force. Since with the braking procedure thereoccurs the production of heat at the brake ring 1, the connectionbetween the brake ring 12 and the hub body 16 must be designed such thata thermal expansion of the brake ring 12 may be effected andsimultaneously a secure and centred seating of the brake ring relativeto the hub body 16 or to the rotational axis of the brake disc isensured. Simultaneously it is desirable for the screws 15 used forconnection of the hub body 16 to the brake ring 12 to be protected frombending stresses in the case of thermal expansion.

[0030] With the brake disc shown in FIG. 1 the connection between thebrake ring 12 and the hub body 16 is effected via a screw 15 whichpasses through an axially parallel opening 114 in the hub flange 14which extends radially (that is to say upwards in the drawing) and whichis integrally formed on the hub body 16. Furthermore the screw passesthrough an axially parallel opening 113 in the brake ring flange 13which is formed on the inner radial edge of the brake ring 12 and isarranged axially neighbouring the hub flange 14. The fixation of thebrake ring 12 on the hub body 16 is effected by a nut 16 placed onto thefree end of the screw 15 and its tightening with a predeterminedtightening torque (typically 36 Nm). At the same time between the nut 19and the brake ring flange 13 there is arranged a sleeve 20 through whichthe screw is guided and which with one end is supported on the brakering flange 13. The nut 19 bears on the other end of the sleeve 20 inorder to indirectly exert the defined pretension force onto the brakering flange 13.

[0031] According to the invention, a retaining lug 17 is arrangedaxially distant to the hub flange 14 on the hub body 16 and comprises anopening which is aligned to the openings in the hub flange 14 and thebrake ring flange 13. The sleeve 20 is guided in the opening of theretaining lug 17 with a tight fit. The retaining lug 17 thus fixes thesleeve 20 with regard to a movement in the radial direction and in thecircumferential direction, by which means simultaneously the free end ofthe screw 15 located in the sleeve 20 is fixed in a correspondingmanner. At the same time however an axially parallel displacement of thesleeve 20 in the opening of the retaining lug 17 is possible, so that ontightening the nut 19 on the screw 15 the sleeve 20 may travel in thedirection of the brake flange 3 and here exert the desired pretensionforce.

[0032] With the described arrangement the two ends of the screw 15 aremounted fixed with respect to the hub body 16 so that the screw 15 mayretain its axially parallel position even with a thermal expansion ofthe brake ring 12. By way of this the loading on the screw and thus thewear and the danger of destruction is reduced. At the same time thesleeve 20 which surrounds the screw 15 to a considerable part of approx.10 to 40% of the axial extension, contributes to a stabilisation withrespect to bending stresses.

[0033] In the design of the screw connection shown in FIG. 1 there isfurthermore provided a radial guide which permits the brake ring 12 togrow radially in the case of thermal expansion and simultaneouslycentres it. Such radial guides are preferably uniformly distributed overthe circumference around the rotational axis of the disc brake, forexample in the form of three radial guides at a distance of in each case120° (cf. FIG. 4, 27a). The radial guide with the embodiment formaccording to FIG. 1 is achieved in that on that end of the sleeve 20which faces the brake ring flange 13 there are provided two milledrecesses lying opposite with respect to the sleeve axis, by way of whichtwo parallel surfaces 10, 10′ are formed on the sleeve 20 (detail A).Furthermore the side of the brake ring flange 13 facing the sleeve 20comprises a milled recess 215 which preferably comprises two parallelsurfaces 10″ formed at an equal distance to the opening for leadingthrough the screw 15. The distance of these surfaces 10″ corresponds tothat of the parallel surfaces 10, 10″. The sleeve fills the spacebetween the milled recesses in the brake ring flange 13. That end of thesleeve 20 which faces the brake ring flange 13 engages into the spaceformed by this milled recess, wherein the chamfered surfaces 10, 10′ ofthe sleeve 20 bear on the planar surfaces 10″ of the milled recess inthe brake ring flange. The cooperation of the sleeve 20 and surfaces 10″thus ensures a guided radial movability between the sleeve 20 and thebrake ring flange 13 in the case of a thermal expansion of the brakering 12.

[0034] The variant shown in FIG. 1 is in particular suitable with theapplication of brake rings 12 of iron. A modification of this embodimentform which is preferably suitable for brake rings 212 of aluminium isshown in FIG. 2. With this on the hub body 16 there is arranged aretaining lug 17 which is axially distanced to the hub flange 14 andwhich comprises an opening concentric to the opening for leading throughthe sleeve 20. The brake ring flange on the side of the retaining lug 17has a cylindrical milled recess. The diameter of this,milled recess islarger than the diameter of the sleeve 10 so that a slide block 18 maybe arranged in the milled recess. The slide block 18 fills the milledrecess in the brake ring flange 213 up to a central groove 118 extendingin the radial direction. That end of the sleeve 20 which faces the brakering flange 213 engages into this groove 118, wherein the chamferedsurfaces 10, 10′ of the sleeve 20 (detail A, FIG. 1) bear on the planarsurfaces 10″ of the groove in the slide block 18 (detail C). Thecooperation of the sleeve 20 and the slide block 18 thus ensures aguided relative movability between the sleeve 20 and slide block 18 inthe case of a thermal expansion, of,the brake ring 212. At the same timethe same parts have been given the same reference numerals as FIG. 1 andare hereinafter not explained again.

[0035] The difference to the embodiment form according to FIG. 1additionally lies in the fact that conical spring washers 21 arearranged between the sleeve 20 and the nut 19, which ensure that adefined axial tension force is exerted between the brake ring flange 213and the hub flange 14 independently of the temperature of the brake ringflange. Furthermore a further washer 11, is arranged between the brakering flange 213 and the hub flange 14.

[0036] As is evident from the FIGS. 1 and 2 one may combine the same hubbody 16 with various brake rings 12, 212. It is indeed a particularadvantage of the present invention that the brake discs may be composedof various components according to requirement in a modular system,without the complete brake disc having to be manufactured again.

[0037] An alternative embodiment form of the screw connection between ahub body 316 and a brake ring 312 of aluminium is shown in FIG. 3. Thesame elements are provided with the same reference numerals as with theembodiment form according to FIG. 1, and are subsequently not explainedagain.

[0038] The essential difference of the embodiment form according to FIG.3 to the previously mentioned embodiment forms lies in the fact that inplace of a retaining lug 17 there is formed a hook-like projection 25 onthe hub body 316 which extends axially parallel and by way of this formsa likewise axially parallel groove 24 towards the hub body 316. One limbof an L-shaped retaining bracket 22 is introduced into this groove 24 sothat the retaining bracket 22 is fixed in the radial direction, but atthe same time remains movable in the axial direction. The second limb ofthe retaining bracket 22 extends radially outwards (in FIG. 3 upwards).This limb lies axially neighbouring the brake ring flange 313 as well asindirectly neighbouring the hub flange 314. That free end of the screw15 which lies opposite the screw head is guided through an opening whichis arranged in the middle of the limb and which is aligned with theopenings in the hub flange 314 and in the brake ring flange 313. The nut19 which via conical spring washers 21 exerts a defined tension force onthe retaining bracket 22 is screwed onto this free end. On account ofits axially moveable mounting the retaining bracket 22 may exert thistension force onto the brake ring flange 313 via the disc 11.

[0039] Furthermore a slide block 23 is arranged between the hub flange314 and the brake ring flange 313, which on the one hand is radiallyguided in a corresponding milled recess in the proximal side of thebrake flange 313 and on the other hand is fixed in a relief of the hubflange 314.

[0040] In FIG. 4 there is represented a lateral view of a brake discwith which the front friction surface of the brake ring 412 is partlybroken. By way of the breaking-up which extends roughly up to the middleplane of the brake ring 412, the connection webs 26 are recognisable insection, which connect the surfaces of the brake ring 412 lying oppositeone another to one another.

[0041] It may further be recognised that the brake ring 412 on its inneredge comprises a brake ring flange in the form of radially inwardlyprojecting lugs 413. These lugs 413 are fastened on corresponding lugs414 on the hub body 416.

[0042] Furthermore it may be recognised from FIG. 4 that there areformed three radial guides 27 a, 27 b, 27 c arranged uniformlydistributed at an angular distance of 120°. In their cooperation thesethree radial guides ensure that the brake ring 412 may move radially andat the same time remains centered with respect to the rotational axis ofthe disc brake in the case of a thermal expansion. The radial guides arerealised in that slide blocks connected to the brake ring flange with apositive fit are arranged in corresponding, radially aligned guidegrooves of the hub flange, or slide blocks connected with a positive fitto the retaining element of the hub 17 are arranged in correspondingradially aligned guide grooves of the brake ring. The remaining screwconnections on all sides are provided with a suitable play so that theyalso permit a radial movement.

[0043] The construction of the screw connections in the brake disc isrecognised from the section shown in FIG. 5 along the line V-V of FIG. 4which is shown running at angles, and FIGS. 6 and 8. The radiallyinwardly directed lugs 413 of the brake ring 412 are connected via ascrew 15′ to the hub lug 414 on the hub body 416, wherein the screw 15′is fixed in a retaining bracket 422 on that end lying opposite the hublug 414. The arrangement thus corresponds essentially to that of FIG. 3,wherein however the short, axially parallel limb of the retainingbracket 422 is arranged rotated by 180° and thus points in the directionof the hub lug 414. It may further be recognised that between the lug413 of the brake ring and the hub lug 414 there is arranged a slideblock 423 which is radialy guided in a radially orientated groove in thelug 414. The manner of functioning of the hook-shaped projection 25′(FIG. 6) and of the axially parallel groove 24′ (FIG. 8) have alreadybeen explained by way of FIG. 3.

[0044] The design of the disc brake according to the invention has theadvantage that one embodiment of the hub body may be combined withvarious brake rings—typically in a diamater range of 590 to over 700 mm.The hub design may just as easily be used with brake rings of differentmaterials, for example Al (aluminium substrate material with frictionsurfaces of metal matrix composite material with SiC particles), CC—SiC(carbon fibre composite material infiltrated with SiC), GG (cast ironwith nodular graphite) or GS (cast steel).

[0045] An assembly of the disc brake is possible without a special toolon account of its simple design. Furthermore by way of the formation oflug connections and the intermediate spaces which remain free there isensured an improved ventilation efficiency which results in a greaterconversion of energy and an extended lining sevice life. With an equalloading therefore an increased serviceable life of the brake ring isachieved.

[0046] List of Reference Numerals:

[0047]10, 10′, 10″ surfaces

[0048]11 disc

[0049]12, 212, 312, 412 brake ring flange

[0050] opening

[0051]14, 314,414 hub flange

[0052]114 opening

[0053]15, 15′ screw

[0054]16, 316, 416 hub body

[0055]17 retaining lug

[0056]18 slide block

[0057]19 nut

[0058]20 sleeve

[0059]21 conical spring washer

[0060]22, 422 retaining bracket

[0061]22, 423 slide block

[0062]24, 24′ groove

[0063]25, 24′ projection

[0064]26 connection web

[0065]27 a, 27 b, 27 c radial guide

[0066]215 milled recess

[0067]118 groove

1. A brake disc for a disc brake, in particular for rail vehicles,containing a hub body (16) with a radially outwardly extending hubflange (14, 314, 414) with axially parallel openings (114) in whichscrews (15, 15′) may be arranged in order to connect a brake ring flange(13, 213, 313, 413) of a brake ring (12, 212, 312, 412) to the hub body(16, 316, 416), said brake ring flange being arranged radiallyoverlapping and axially adjacent the hub body, wherein with at least oneopening (114) there is arranged a retaining element (17, 22, 422) whichis fixed on the hub body (16, 316, 416) and by way of which the end ofthe screw (15, 15′) may be held after its passage through the brake ringflange (13, 213, 313, 413), characterised in that at least one of theretaining elements is formed as an L-shaped retaining bracket (22, 422)which in a first limb comprises an opening for leading through the endof the screw (15, 15′), and that on the hub body (316, 416) there isprovided an axially orientated groove (24, 24′) in which the second limbof the retaining bracket (22) is arranged.
 2. A brake disc according toclaim 1, characterised in that on the hub flange (314, 414) and/or onthe retaining elements (17) there are provided at least three radialguides (27 a, 27 b, 27 c) which are arranged uniformly distributed overthe circumference and which may cooperate with corresponding radialguides on the brake ring flange (13, 213, 313, 413) in order to radiallyguide and centre the brake ring flange in the case of thermal expansion3. A brake disc according to claim 2, characterised in that the radialguides (27 a, 27 b, 27 c) in each case are formed as two surfacesextending parallel to a radius, on the hub flange (314, 414) and/or on aretaining element (17 with 20), which cooperate with correspondingsurfaces on the brake ring flange (13, 213, 313, 413).
 4. A brake disc,in particular for rail vehicles, containing a hub body (16, 316, 416) aswell as a brake ring (12, 212, 312, 412) fastened on this, characterisedin that the hub body (16, 316,416) is designed according to one of theclaims 1 to 3, and that the end of the screw (15, 15′) is held by theretaining element (17, 22, 422) fixed on the hub body
 5. A brake discfor rail vehicles according to one of the claims 1 to 4, characterisedin that the screw (15, 15′) is formed in a manner such that the head ofthe screw (15, 15′) comprises a surface which by way of its bearing on acollar of the hub specially formed as a support there is effected arotational a securement when screwing on and off the nut and below thehead there is incorporated a knurling which on assembly of the screw(15, 15′) into the hub digs into the receiver bore and by way of this(15, 15′) firmly retains the screw (15, 15′) in the hub with a firmpress fit.